Aluminum bronze alloy containing manganese and having improved wear resistance



United States Patent ALUMINUM BRONZE ALLOY'CONTAINING MAN- GANESE AND HAVING IMPROVED WEAR RE- SISTANCE John F. Klement, Milwaukee, Wis., assignor to Ampco Metal, Inc., Milwaukee, Wis., a corporation of Wisconsin V No Drawing- Application October 1, 1957 Serial No. 687,364, 1

9 Claims. (Cl. 75-161) This invention relates to an aluminum bronze alloy and. more particularly to an aluminum bronze alloy having improved toughness and wear resistance.

Aluminum bronze alloys have for years been used as dies for forming and drawing operations for a large group 2,874,042 Patented Feb. 17, 1959 '2 The wear test results of the above table were obtained on a rolling-slip friction device, such as an Amsler wear test machine. In these tests the aluminum bronze alloy cylindrical test specimens were subjected to rolling and sliding motions against stainless steel cylinders with an applied compressive stress of 31,500 p. s. i. on the specimens. The test specimens 1, 2 and 3, in the table, contain of sheet and plate alloys such as stainless steel, aluminum,

nickel, titanium, mild steel and some copper base alloys. Aluminum bronze alloys used in die applications possess the properties of good corrosion resistance, wear resistance, and non-galling against many wrought materials.

The aluminum bronze alloys which, in, the past have shown the optimum properties for deep drawing dies are those that contain approximately 14% aluminum, a small amount of iron, and the balance copper. An alloy of this type has good corrosion resistance and non-galling properties. However, under heavy use in die application, it wears undesirably fast so that close dimensional tolerances cannot be maintained because of the wear that occurs on the die surface.

The-present invention is directed to an aluminum bronze alloy which has the corrosion resistance and the nongalling properties characteristic of aluminum bronze alloys buthas greatly improved wear resistance and toughness.

The'aluminum bronze alloy of the invention has high uniform hardness, good toughness, excellent wear resistance and improved machinability. This isaccomplished by the addition of a small amount of manganese which renders the alloy less susceptible to eutectoid transformation and its embrittling structure.

only iron and aluminum in combination with copper and have a substantially lower resistance to wear than specimen number 4 which falls within the scope of the present invention. The increase in wear resistance due to the addition of manganese to aluminum bronze is most significant since the hardness of all specimens is substantially the same.:

With the manganese addition to aluminum bronze alloys the wear rate of the alloy against stainless type steels will be less than 0.00500 gram per 1000 meter kilogram (m. k. g.) frictional work as measured by an Amsler wear testing machine and generally in the range of 0.00350 to 0.00450 gram per 1000 meter kilogram (m. k. g.) of frictional Work.

In addition, the alloy has a hardness in the range of 25 Rockwell C to 55 Rockwell C, depending upon the specific aluminum and manganese contents in the alloy.

In addition to substantially increasing the wear resistance of the alloy the manganese also makes the alloy less susceptible to the eutectoid transformation. The eutectoid structure consists of alpha phase plus gamma two phase formed from the transformation-decomposition of the beta phase. This transformation occurs at temperatures below 1050 F. in aluminum bronze alloys and the resultant eutectoid structure is brittle and possesses 10w ductility and poor machinability. I

The alloy of the invention containing about 14.5% aluminum, 4.5% iron, and3.0% manganese with balance being substantially copper can be cast either statically or centrifugally to produce a fine grained tough structure The alloy of this invention has the following general composition by weight: 1

Percent Aluminum L s 13.0-20.0 Iron 1.0-8.0 Manganese 1.0-8.0 Copper Balance A specific illustration of the composition of the alloy ofthe invention falling'within'the above range is.as follows in weight percent:

Percent Aluminum 14.37 Iron 4 4.65 Manganese 3.00 Copper 77 .98

- The wear resistance of an alloy of the invention containing manganese as compared with that of an ordinary aluminum bronze alloy is illustrated in the followingtable:.

having a hardness of approximately 39 Rockwell C. This alloy displays unusual compressive strength and test specimens have registered close to 200,000 p. s. i. in ultimate compression.

The metallographic structure of the above alloy consists essentially of gamma two phase which is uniformly distributed in a matrix of beta. An intermetallic'compound composed of iron, aluminum, copper and manganese exists in particle form with some rosette shaped particles. Because of the method of casting andthe inoculent used, the intermetallic compound is uniformly distributed throughout the cast section.

In order to obtain optimum properties, the metals used for the alloy should be of highquality. Electrolytic or wrought fire refined copper, high purity aluminum, low

carbon iron, and high purity manganese are preferred to be used. It has also been found that a very satisfactory method of obtaining the desired uniformity in the alloy,

7 iron and 10% manganese.

The melting procedure employed in making the prealloy is such that some copper, along with the iron and manganese, is placed into the crucible and melting begun. When the copper starts to melt, the iron and other additives are slowly dissolved into the copper during that period when aluminum is added to form an exothermic reaction which helps to dissolve the higher melting point manganese addition. This pre-alloy is then cast into ingot form and is ready to use for the 'final alloy.

Alternately, instead of adding the manganese to the pre-alloy, the manganese can be added to the final alloy.

To establish complete uniformity of the microstructure and hardness the alloy is heat treated at an elevated temperature in the temperature range of 1050 F. to 1400 R, such as about 1150 F. Small castings of simple shapes of this alloy can be placed directly into the heat treating furnace at temperature. Large massive castings or intricate shapes are preheated in the furnace at about 400 F. until the section reaches uniform temperature and then are heated directly to the elevated temperature. The castings are held at a temperature in the range of 1050 F. to 1400" F. for one hour plus one-half hour per inch of section thickness greater than one inch, up toa maximum of two and one-half hours at temperature. 7

After the required soaking time at the elevated temperature, the alloy is cooled at a rate faster than about 20 F. per hour per one inch of section thickness. This rate is conveniently obtained by fan air cooling.

Internal stresses created within castings during machining or other finishing operations, during weldments, or from metal overlays on base metals, are usually removed depending on the future application of the part. These stresses are removed by a stress relief heat treatment. The usual commercial aluminum bronze alloys cannot generally be stress relieved at a temperature in the range of 650 F. to 1050 F. due to eutectoid formation that occurs at this temperature range. Furthermore, a stress relief at temperatures above 1050 F. frequently causes distortions and further stresses in the usual commercial aluminum bronze alloy during the rapid cooling to room temperature. Stress relief at temperatures lower than 650 F. takes considerabletime and often the most severe stresses remain.

In contrast to this, the alloy of the invention can be stress relieved within the temperature range of 650 F. to 1050 F. without embrittlement due to the excessive eutectoid structure. An optimum stress relief temperature for the present alloy, based on the severity of the internal stresses and geometry of the article, can be selected in the range of 650 F. to 1050 F. to obtain a reasonable holding time in the furnace, such as one to two hours per 2 inches of section, and to prevent distortions and micro stresses during cooling. The article is then cooled to room temperature.

Small amounts of metals, such as tin, zinc, lead, nickel,

silicon and beryllium can be present in the alloy up to about 1% by weight without adversely afiecting the characteristics ofthe present alloy. The alloy of this invention can be used to produce articles that require corrosion resistance, toughness, and exceptional wearing properties. The articles may take the form of deep drawing dies, wear guides, forming rolls, etc.

The alloy can also be extruded into weldrods or weld wire. The alloy in the form of coated or uncoated weldrod can be overlaid on a base metal by metal sprayingor other welding methods, such as heli-arc, metalarc, carbon-arc, etc. to obtain a corrosion resistant wear surface. The metal overlay can be given a stress relief treatment at temperatures in the range of 650 F. to 1150 F. and cooled to room temperature.

It has been found that the addition of manganese to the copper-aluminum-iron alloys 'to be used as die mate rials greatly improves the toughness and wear resistance of the alloy and makes it less susceptible to eutectoid embrittlement.

In addition, the alloy of the invention has not only increased toughness, strength, and wear resistance but also has improved machinability by controlling the distribution of the'various component phases. The improved machinability permits die sinking of more intricate designs on die surfaces'than was previously possible on ordinary aluminum bronze die alloys.

Various modes of carrying out the invention are contemplatedas being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

Iclaim:

1. An aluminum bronze alloy, consisting essentially of 13% to aluminum, from 1% to 8% iron, from 1.0% to 8.0% manganese, and the balance being substantially copper, said alloy being characterized by having excellent corrosion resistance and having improved toughness and wear resistance. r a

2. An aluminum bronze alloy consisting essentially of from 13% to20% aluminum, from 1% to 8% iron, from 1.0% to 8.0% manganese, and the balance being substantially copper, the said alloy having a wear rate of less than 0.005 gram per 1000 meter kilograms of frictional work as measured on arolling-slip wear testing machine.

3, An aluminum bronze alloy consisting essentially of from 13% to 20% aluminum, from 1% to 8% iron, from 1.0%'to 8.0% manganese, and the balance being substantially copper, said alloy havinga wear rate of less than 0.005 gram per 1000 meter kilograms of frictional work as measured on a rolling-slip wear testing machine and having a hardness in the range of 25 to 55 Rockwell C.

4. An aluminum bronze alloy having improved toughness and wear resistance consisting essentially of 14.37% aluminum, 4.65% iron, 3.00% manganese, and 77.98% copper.

5. An aluminum bronze alloy having improved toughness and wear resistance, consisting essentially of 13% to 20% aluminum, from 1% to 8% iron, from 1.0%

to 8.0% manganese, and the balance being substantially copper, said alloy having improved homogeneity of structure and uniformity of harness by heating the alloy to a temperature of 1150 F. and thereafter cooling the alloy at a rate faster than 20 F. per hour per one inch of section thickness to room temperature.

6. An article of manufacture characterized by having excellent corrosion resistance, a hardness in the range of 25 to 55 Rockwell C and a wear rate of less than 0.005 gram per 1000 meter kilograms of frictional work as measured by a rolling slip wear testing machine, said to 8% iron, 1.0% to 8.0% manganese and the balance copper to establish uniformity of the microstructure and hardness in the alloy, comprising heating the alloy to a temperature in the range of 1050" F. to 1400 F., retaining said alloy at said temperature for a period of one hour plus one-half hour per inch of section thickness greater than one inch up to a maximum period of two and one-half hours, and cooling the alloy from said temperature at a rate faster than 20 F. per hour per one inch of section thickness to room temperature.

9. A method of heat treating an aluminum bronze alloy consisting essentially of 13% to 20% aluminum, 1% to 8% iron, 1.0% to 8.0% manganese and the balance copper to establish uniformity of the microstructure and hardness in the alloy, comprising heating the alloy to a temperature in the range of 1050 F. to 1400 F., retaining said alloy at said temperature for a period of one hour plus one-half hour per inch of section thickness greater than one inch up to a maximum period of two and one half hours, cooling the alloy from said temperature at a rate faster than 20 F. per hour per one inch of section thickness to room temperature, stress relieving the alloy by heating the alloy to a temperature in the range of 650 F. to 1050" F., and thereafter cooling the alloy to room temperature.

No references cited. 

5. AN ALUMINUM BRONZE ALLOY HAVING IMPROVED TOUGHNESS AND WEAR RESISTANCE, CONSISTING ESSENTIALLY OF 13% TO 20% ALUMINUM, FROM 1% TO 8% IRON, FROM 1.0% TO 8.0% MANGANESE, AND THE BALANCE BEING SUBSTANTIALLY COPPER, SAID ALLOY HAVING IMPROVED HOMOGENEITY O STRUCTURE AND UNIFORMITY OF HARNESS BY HEATING THE ALLOY TO A TEMPERATURE AT 1150* F. AND THEREAFTER COOLING THE ALLOY AT A RATE FASTER THAN 20* F. PER HOUR PER ONE INCH OF SECTION THICKNESS TO ROOM TEMPERATURE. 